Methods for manufacturing ultrahard compacts

ABSTRACT

A method for manufacturing an ultrahard compact includes assembling a mass of ultrahard material with a mass of substrate material such that the mass of ultrahard material extends radially outward a greater extent than the substrate material to compensate for a difference in the radial shrinkage of the ultrahard material compared to the substrate material during a sintering process. The method may further includes subjecting the assembled compact to a high pressure high temperature process mat results in the forming of an ultrahard compact including an ultrahard layer integrally bonded with a substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/858,662filed Jun. 1, 2004, which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF INVENTION

1. Field of the Invention

This invention relates to ultrahard compacts, and more specifically toultrahard compacts including ultrahard material integrally formed with asubstrate. The invention also relates to improved methods for formingsuch ultrahard compacts.

2. Background Art

Ultrahard compacts typically comprise a body of ultrahard materialbonded to a substrate. Examples of ultrahard materials includepolycrystalline diamond (PCD) and cubic boron nitride (CBN). Substratesof ultrahard compacts typically are formed from a carbide material, suchas tungsten carbide cemented with cobalt. Ultrahard compacts are wellknow for their mechanical properties of high wear resistance making thema popular choice for use as cutting elements in industrial applications,such as in cutting tools for machining and for subterranean mining anddrilling tools.

Ultrahard compacts are typically formed by loading a can assembly withultrahard material particles and substrate material and men subjectingthe assembly to a high pressure high temperature (HPHT) pressing processthat results in the sintering of the ultrahard material particles andbonding of the ultrahard material to the substrate. Methods for makingultrahard compacts are more fully described in U.S. Pat. Nos. 3,609,818;3,743,489; 3,745,623; 3,850,591; 4,403,015; 4,954,139; and 6,610,095,the disclosures of which are expressly incorporated herein by reference.

Ultrahard compacts used for cutting tools and drilling tools are mostcommonly made in the form of a cylindrical member as illustrated inFIG. 1. The refractory metal containers used to form these compacts havecylindrical walls of uniform internal diameter along the length of thecan. Ultrahard compacts produced in these types of cans have been foundto have as much as a 20% to 30% difference in radial shrinkage betweenultrahard material and substrate material when the compact is retrievedfrom the can after a pressing process. This has been found to beespecially true for compacts formed with thicker ultrahard materiallayers, such as layers 1.0 millimeters (mm) or more in thickness. Thisis also particularly true for ultrahard compacts that are sintered in ahigh pressure high temperature apparatus known as a cubic press,although similar issues exist when compacts are formed using other typesof presses, such as a belt press. The difference in radial shrinkage isbelieved to be due to differences in the shrinkage and consolidation ofthe different materials.

Ultrahard compacts, especially those with thick ultrahard layers, aretypically tapered in form when recovered from the press, as illustratedfor example in FIG. 4. The layer of ultrahard material 42 in thesecompacts 40 is tapered such that the ultrahard material nearest thesubstrate 44 (proximal interface 43) has the largest diameter and theultrahard material furthest away from the substrate 44 has the smallestdiameter. To obtain an ultrahard compact having a final desired uniformshape, these compacts 40 must be ground after the HPHT pressing processto bring the ultrahard material 42 and the substrate 44 to the samedesired diameter 46 along the entire length of the compact 40. Thethicker the body of ultrahard material 42 is on the substrate 44, themore pronounced the taper will be after the pressing operation, and themore grinding required to obtain a final uniform product.

Following conventional methods of manufacturing compacts as describedabove, the cost associated with centerless grinding of a compact with adiamond wheel to produce a final uniform product can be as much as 20%to 40% or more of the overall cost of the product, depending on thethickness of the ultrahard material body and the type and composition ofthe ultrahard material used to form a compact. Reducing the amount ofcenterless grinding required to manufacture an ultrahard compact ofdesired shape can result in a substantial cost saying due to a reductionin the number of grinding wheels required to finish products and in thetime spent grinding and finishing products. Therefore, a method formanufacturing ultrahard compacts that reduces the amount of grinding andfinishing required to obtain a final product is desired.

SUMMARY OF INVENTION

In one aspect, the invention provides a method for manufacturing anultrahard compact. In one or more embodiments, the method includesassembling a mass of ultrahard material assembled with a mass ofsubstrate material to form a pre-sintered compact. The mass of ultrahardmaterial is formed to extend further from a central axis that the massof substrate material. The mass of substrate material is formed toextend to form at least a part of the side surface of the pre-sinteredcompact. The method may further include subjecting the pre-sinteredcompact to a high pressure, high temperature pressing process that formsthe ultrahard compact including a layer of ultrahard material integrallyformed with a substrate.

In another aspect, the invention provides a container assembly forforming a compact. The container assembly includes a generallycylindrical container having an internal diameter that varies along itslength, generally defining a first section and a second section in thecontainer. At least one end of the container is opened to allowplacement of material therein. A diameter of the container in the firstsection is between about 2% and 20% larger than a diameter of thecontainer in the second section. The second section is between 8 mm and80 mm in diameter. The height (or length) of the first section is atleast about 1.0 mm.

In another aspect, the method provides a pre-sintered compact. In oneembodiment, the compact includes a mass of ultrahard material and a massof substrate material. The mass of ultrahard material is assembled withthe mass of substrate material such that the mass of ultrahard materialextends an additional amount further from a central axis than the massof substrate material. The mass of substrate material extends to form atleast part of the side surface of the compact.

In another aspect, the invention provides a method for a container. Inone embodiment, the method includes placing a mass of ultrahard materialin a first section of a container and placing the first section of thecontainer in a forming die. The method further includes extending aforce on the mass of ultrahard material to force a side wall of thecontainer to expand outward such that the side wall extends further inthe first section than in the second section.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows one example of an ultrahard compact that may be formed inaccordance with an embodiment of the present invention.

FIG. 2 shows a schematic view of a cubic press used for sinteringultrahard compacts.

FIG. 3 shows a cross-section view of the cubic cell shown in FIG. 2.

FIG. 4 shows a cross-section view of an ultrahard compact retrievedafter a pressing process that has been formed in accordance withconventional methods for forming a compact.

FIG. 5 shows one example of a container assembly in accordance with anembodiment of the present invention.

FIG. 6 shows one example of a method for forming the container assemblyshown in FIG. 5 and pre-forming an ultrahard compact in accordance withan embodiment of the present invention;

FIG. 7 shows another example of a method for forming a containerassembly as shown in FIG. 5 and pre-forming an ultrahard compact inaccordance with an embodiment of the present invention.

FIG. 8 shows a cross-section view of a pre-formed compact in accordancewith one embodiment of the present invention.

FIG. 9 shows a cross-section view of an ultrahard compact retrievedafter a pressing process that has been pre-formed in accordance with anembodiment of the present invention.

FIG. 10 shows another example of a container assembly in accordance withan embodiment of the present invention wherein the first section of thecontainer assembly expands radially outward in a direction away from afirst section.

FIG. 11 shows another example of a container assembly in accordance withan embodiment of the present invention, wherein a first section isdisposed between second sections.

FIG. 12 shows another example of a container assembly in accordance withan embodiment of the present invention, where a second section isdisposed; between first sections.

FIG. 13 shows one example of a compact including multiple ultrahardmaterial masses formed with a substrate.

FIG. 14 shows one embodiment of a container that may be used to form acompact as shown in FIG. 13.

FIG. 15 shows one example of a drilling tool which includes one or moreultrahard compacts formed in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

The present invention relates to an improved container assembly forforming ultrahard compacts, as well as methods for forming ultrahardcompacts and ultrahard compacts formed by such methods. The inventionalso relates to cutting tools and drilling tools having one or moreultrahard compacts formed in accordance with embodiments of the presentinvention.

One example of an ultrahard compact that may be formed in accordancewith ah embodiment of the invention is shown in FIG. 1. In this example,the compact 10 is generally cylindrical in shape and includes anultrahard layer 12 bonded onto a substrate 14. The ultrahard layer 12may be formed of any ultrahard material known in the art, such aspolycrystalline diamond (PCD), cubic boron nitride (CBN). The substrate14 may be formed of any metal carbide known in the art, such as tungstencarbide with cobalt binder. This type of compact 10 may be used as acutting element for an earth boring bit or other cutting tool.

An ultrahard compact as shown in FIG. 1 is typically formed by placing amass of ultrahard material and a mass of substrate material in acontainer assembly for pre-forming a compact and then subjecting theloaded container assembly to a high pressure, high temperature (HPHT)pressing process that causes crystalline bonds to form between ultrahardparticles and ultrahard material to bond to the substrate. The ultrahardmaterial loaded into the container assembly before the pressing processmay be a mass of ultrahard material particles or a previously sinteredgranulated mass of ultrahard material. Similarly, the substrate materialmay be in the form of metal particles infiltrated with binder or apreviously formed solid metal carbide body. Numerous other variationsare also well known in the art for forming ultrahard compacts. The abovedescription is provided for illustrative purposes and is not intended tolimit the invention.

FIG. 2 shows one example of a press that can be used to carry out HPHTprocesses for forming ultrahard compacts. This type of press is known asa Cubic press 20. The press is used to subject a loaded containerassembly to high pressure and high temperature conditions for a timesufficient to produce the desired bonding of the compact material toform an integral ultrahard compact. Operational techniques forsimultaneously applying high pressures and high temperatures in this andsimilar types of presses, such as a belt press, are well known in theart and not repeated here.

As shown in FIG. 2, the cubic press 20 includes six anvils 22 which arearranged in opposing pairs for rectilinear movement along three mutuallyperpendicular coordinate axes. The anvils 22 include sloping shouldersthat terminate in equal area square faces 24. Each of die anvils 22 isattached to and powered by support apparatus (not shown) which includesa double acting hydraulic ram affixed to a base. The motion of theanvils 22 is synchronized by an anvil guide mechanism (not shown), suchthat the thrust of the six rams simultaneously moves the anvils 22toward a symmetry center of the press 20 to engage a reaction cell 30containing one or more container assemblies filled with compactmaterial. The reaction cell 30 in the press 20 has square faces that areset parallel to and are greater in area than the corresponding anvilfaces 24. The outer body of the reaction cell 30 is formed of a pressuretransfer medium, such as pyrophillite or another appropriate pressuretransfer material able to undergo the pressures applied by the cubicpress 20.

During a pressing process, the anvils 22 advance and engage with thereaction cell 30 to extrude and compress the reaction cell 30 betweenthe sipping shoulders of the anvils 22. The forced engagement of theanvil faces 24 with the reaction cell 30 generates pressure on thereaction cell 30 which is transferred to the one or more compactassemblies contained in the reaction cell 30. As the reaction cell 30 isbeing pressed, heat is generated in the reaction cell 30 by passingelectric current through the anvils 22 to a heating unit in the reactioncell 30.

A cross-section view of one example of a reaction cell 30 is shown inFIG. 3. The outer body 31 of the reaction cell 30 is formed of apressure transfer medium, such as pyrophillite. The body 31 has acentral cavity formed therein to permit placement of a loaded containerassembly 32 in the body 31 of the reaction cell 30. An electricalresistance heating tube 33 is disposed in the central cavity of thereaction cell 30. The heating tube 33 may be formed of any suitable highelectrical resistant material, such as solid or foil graphite, amorphouscarbon, pyrolytic carbon, refractory metals or high electrical resistantmetals. A non-electrically conductive liner 34 is disposed in theheating tube 33. The loaded container assembly 32 is disposed in theheating tube 33, surrounded by the liner 34. Non-electrically conductivediscs 35 are disposed at each end of the liner 34 enclosing the loadedcontainer assembly 32 in non-electrically conductive material, such aswhite salt (NaCl) compressed to 90% or more of its theoretical densityto preserve high pressures of the sintering system and to maintain goodgeometrical stability of the manufactured part. Electrically conductivedisks 36 are disposed oh the exterior sides of the non-conductive disc35 in electrical communication with the heating tube 33 to provide anelectrical connection to the heating tube 33. An end can assemblyincluding an non-conductive end plug 37 formed of a pressuretransferring medium surrounded by an electrical conducting ring 38 isdisposed adjacent each conductive disk 36 to enclose the loadedcontainer assembly 32 in the central cavity of the reaction cell 30while providing an electrical connection to the heating tube 33. Theconductive discs 36 and the conductive rings 38 may be formed of anysuitable electrically conductive material, such as metal. Thenon-conductive liner 34, non-conductive discs 35, and non-conductive endplugs 37 may be formed of any suitable pressure transferring andelectrically insulating medium, such as sodium chloride, pyrophillite, asuitable synthetic substitute for pyrophillite, talc, or hexagonal boronnitride.

The loaded container assembly 32 disposed in the reaction cell 30includes a conventional cylindrical container assembly 32 a which has aconstant radius along its length. The container assembly 32 a is formedof a refractory metal material, such as molybdenum, zirconium, tantalum,hafnium, tungsten, or niobium. The container assembly 32 a is loadedwith a mass of ultrahard material particles 32 b and substrate material32 c. Binder material may be premixed with the ultrahard materialparticles 32 b. Other materials (not shown) may also be included in theloaded container assembly 32, such as one or more layers of transitionmaterial disposed between the ultrahard material particles 32 b and thesubstrate material 32 c.

During a pressing process, the reaction cell 30 undergoes pressureexerted by the anvils (22 in FIG. 2) of the press (20 in FIG. 2). Duringthe pressing process, heat is generated in the reaction cell 30 bypassing an electric current through the anvils (22 in FIG. 2) to themetal rings 38, metal discs 36, and the heating tube 33 which is formedof a highly electrically resistive material, such as graphite. Thispassing of electrical current to the heating tube 33 results in diegeneration of heat in the cavity of the reaction cell 30. The liner 34disposed between in heating tube 33 around the loaded container assembly32 allows heat and pressure to be transferred to the loaded containerassembly 32 while electrically insulating the container 32 a of theassembly from the heating tube 33. After a time sufficient for formingdesired bonds between compact materials, the electrical current isceased, the temperature in the reaction cell 30 is reduced, and thepressure on the reaction cell 30 is removed. The reaction cell 30 isthen removed from the press (20 in FIG. 2), cracked open, and the loadedcontainer assembly 32 is removed.

FIG. 4 shows one example of a compact 40 formed using a conventionalcylindrical container assembly with a constant radius along its length(as shown at 32 a in FIG. 2). This compact was formed with a thickultrahard layer 42 bonded to a substrate 44. The shape of the compact 40out of the press is tapered in form as discussed in the Backgroundsection herein. The material to be removed 48 from the compact to obtaina desired geometry 46 is significant, and will require a significantamount of grinding with diamond wheels to achieve the desired form.

Pre-Formed Compact

In one aspect, the present invention provides a method for forming anultrahard compact which includes forming a mass of ultrahard materialplaced with substrate material such that the mass of ultrahard materialis radially oversized with respect to the substrate material prior to apressing process so sufficient ultrahard material is provided tocompensate for a greater radial shrinkage that occurs in ultrahardmaterial versus substrate material during the pressing process.Pre-forming an ultrahard compact in this way, advantageously, can resultin the production of an ultrahard compact from the press having a thickultrahard layer that is close to a desired uniform geometry with thesubstrate such that the amount of grinding required to produce a finalproduct is reduced.

Container Assembly

In another aspect, the present invention provides a container assemblyfor performing a compact. Referring to FIG. 5, in one embodiment thecontainer assembly 50 includes a container 58 having side walls 57adapted to define at least one first section 51 and at least one secondsection 53, wherein the first section 51 is configured to have aninternal profile that extends further radially outward (in a planegenerally perpendicular to a longitudinal axis 54) than the internalprofile of the second section 53. The first section 51 is adapted toform ultrahard material for a compact. The second section 53 is adaptedto form substrate material for the compact. The first section 51 isexpanded radially outward a greater extent than the second section 53 topermit placement of additional ultrahard material with the substratematerial to compensate for differences in radial shrinkage, includingconsolidation, that occur in ultrahard material versus substratematerial when the compact materials are subjected to a pressing process.

Referring to FIG. 5, in one or more embodiments, the container assembly50 may include a container 58 with at least one end cap 59 adapted tocouple with an open end of the container 58 to form an enclosed vessel.The container assembly 50 generally includes a first end 55, a secondend 56 and side walls 57. The side walls 57 are contoured to define aninternal profile of the container assembly 50 that changes in radialextent along the length of the container assembly 50 to form at leastone first section 51 that bulges outward a further distance from alongitudinal axis 54 than at least one second section 53 to permitplacement of an oversized mass of ultrahard material with the substratematerial in the container assembly 50 to compensate for differences inshrinkage of the materials during sintering. A container assembly inaccordance with an embodiment of the invention may be formed of anysuitable refractory metal, including niobium, tantalum, tungsten,molybdenum, zirconium, hafnium, and titanium.

A container assembly as described above may be used to form compact. Thecompact may be formed by first placing a mass of ultrahard material inthe first section 51 of the container assembly 50; the container 58 ofthe container assembly 50 being positioned as shown so that material canbe loaded therein. The ultrahard material may be in the form of anultrahard material particles or a previously sintered granulated mass.The ultrahard material may be packed or pre-pressed into the firstsection 51 to eliminate voids in the first section 51. Substratematerial is then placed on top of the ultrahard material. The compactmaterials are then enclosed in the container assembly 50 by placing theend cap 59 over the exposed end of the substrate and in engagement withthe open end of the container 58. The container assembly may then bepressed together to further compact the materials therein, eliminatingvoids, and create sealing engagement between the container 58 and thenend cap 59 of the container assembly 50.

A container assembly contoured in accordance with one or moreembodiments of the invention may be particularly desired for themanufacture of compacts haying thicker ultrahard layers, such as layersat least 1.0 millimeters (mm) thick or more, to allow for the productionof ultrahard compacts from the pressing process having closer to desireduniform geometries. Forming a compact in accordance with one or moreembodiments of the invention as described above, advantageously, canreduce the amount of grinding required to obtain a final product. Theamount of grinding required may be reduced by 15%, and in some cases byas much as 30%. In the production of compacts with thicker diamondtables, the reduction in the material to be removed may be as much as50% or more. Reducing the amount of grinding required can significantreduce manufacturing costs for ultrahard compacts because diamondgrinding wheels required for grinding compacts to desired geometries arevery expensive. Additionally, because the ultrahard material beingground is very hard, grinding to a final desired geometry can be verytime consuming. This is especially true for compacts having thickerultrahard layers. Therefore, providing a method and apparatus that canbe used to reduce the amount of grinding required to produce finalproducts can result in a significant cost savings and time savings inmanufacturing ultrahard compacts. In particular, the number of diamondwheels required to produce such compacts can be significantly reduced.

Forming a Container Assembly

In another embodiment, the invention also provides a method for forminga container assembly. In one embodiment, the method includes forming acontainer assembly such that the walls inside the container assembly arebulged out in a first section a greater distance from a longitudinalaxis than the walls in a second section of the container assembly topermit the placement of a radially larger mass of ultrahard material inthe container assembly than the substrate material. The ultrahardmaterial can then be loaded in the first section, and substrate materialloaded in the second section of the container. The ultrahard materialand substrate material can then be enclosed in the container assembly.The loaded container assembly can then be subjected to a high pressurehigh temperature sintering process sufficient to integrally form anultrahard compact including an ultrahard layer of material integrallyformed with a substrate.

One example of a method that may be used to form a container assembly inaccordance with an embodiment of the present invention is shown in FIG.6. In this example a section of a conventional refractory metalcontainer 63 is expanded radially outward in a forming die 64 to producea formed container 66 in accordance with an embodiment of the invention.The forming die 64 is formed of a hard material, such as hardened steelor sintered carbide, and adapted with an internal geometry correspondingto the desired geometry of the formed container. A forming button 65,also formed of a hard material, such as a hardened steel or sinteredcarbide, is positioned at one end of the forming die 64 adjacent thedesired bulged section of the forming die 64. The container 63 is placedon the forming button 65 in the forming die 64 with the section of thecontainer 63 to be expanded radially outward disposed in the radiallylarger section of the forming die 64. Ah elastomer material 62 is placedin the container 63 and a punch 61, made of a hard material such as ahardened steel of sintered carbide, is used to provide loading on theelastomer material 62 placed in the container 63 which forces thecontainer 63 to expand radially outward to form the desired shapedefined by the forming die 64. After the container 63 is formed, theforming button 65 is removed from the larger end of the forming die 64and the formed refractory metal container 66 is retrieved.

After the formed container 66 is retrieved from the die 64, the formedcontainer 66 can be loaded with ultrahard material 69 in the radiallyexpanded section of the container 66. A carbide substrate 68 is thenplaced on top of the ultrahard material 69 and the end cap 67 placedover the end of the substrate 68 in overlapping engagement with theopened end of the formed container 66 to enclose the ultrahard material69 and substrate material 68 in the container assembly. Once the loadedcontainer assembly is formed, the loaded container assembly may bepre-pressed to remove voids or trapped air and, then, loaded into apress and subjected to a HPHT pressing process that results in sinteringof the ultrahard material and bonding of the ultrahard material to thesubstrate.

Another example of a method that may be used to form a containerassembly in accordance with an embodiment of the present invention isshown in FIG. 7. In this example, a conventional refractory metalcontainer 73 is loaded with a mass of ultrahard material 79 in the formof particles or granules pre mixed with binder. A carbide substrate 78is then placed on the mass of ultrahard material 79. The loadedcontainer 73 is placed in the forming die 74 against a forming button 75that supports the container 73. A punch 71 is then used to punch thecontainer 73 into the shape defined by the forming die 74 by impactingthe material in the container 73 with a load that forces the ultrahardmaterial to displace, where possible, radially outward, which causingthe container to expand outward in the section of the containercontaining the ultrahard material 79. Once formed, loaded container 72is retrieved from the die 74 by removing the forming button 75 from thelarger end of the die 74. The end cap 77 for the container 76 is thenplaced on the loaded container 72 in overlapping engagement with theopen end of the formed container 76 to enclose the compact material inthe container assembly. Once the loaded container assembly is assembled,it may be pre-pressed to remove voids and trapped air and then loadedinto a press and subjected to a HPHT process that results in theformation of an integrally formed ultrahard compact of substantiallyuniform shape.

Forming a Compact

In another aspect, the invention provides a method for forming a compactin a pre-sintered state to produce an ultrahard compact in a HPHTprocess haying an “out-of-press” geometry (i.e., geometry produced fromthe press) that is closer to a desired net shape than if the compactwere produced using a conventional container assembly. Such methods maybe particularly useful for forming ultrahard compacts having thickerdiamond tables, such as diamond tables 1.0 mm or more, and morepreferably 1.5 mm or more in thickness.

A cross sectional view of a pre-sintered compact formed in accordancewith one embodiment of the invention is shown in FIG. 8. Thepre-sintered compact 80 includes a container 88 used to form ultrahardmaterial 82 and substrate material 84. The pre-sintered compact 80 alsoincludes a mass of ultrahard material 82 and a mass of substratematerial 84 which are loaded in the container 88. The container 88 hasan internal geometry defined by side walls 87 which are adapted topermit the placement of a radially larger mass of ultrahard material 82in the container 88 with the substrate material 84 so that additionalultrahard material is provided in a bulged portion 85 of the container88 to compensate for the greater radial shrinkage of ultrahard material82 with respect to substrate material 84 when die pre-sintered compact80 is subjected to a HPHT pressing process to sinter the compact 88. Theside walls 87 are shaped to form at least one first section 81 and atleast one second section 83 in the container 88. The first section 81has an internal volume that is expanded radially outward with respect tothe internal volume of the second section 83. The first section 81 maybe generally described as a section of the container having an internalcross section (in a plane perpendicular to the view shown) at a pointalong the longitudinal axis that is generally similar in form, butlarger in size than the internal cross section of the second section 83.

The ultrahard material 82 placed in the first section 81 of thecontainer 88 may be in the form of ultrahard material particles. Forexample, the ultrahard material 82 may comprise diamond powder. Thesubstrate material 84 loaded in the second section 83 of die container88 may comprise, for example, an integral tungsten carbide substrateinfiltrated with binder, such as cobalt, nickel or iron. In otherembodiments, the compact material may be any material known in the artfor forming an ultrahard compact. The pre-sintered material can beenclosed in the container 88 by placing an end cap (such as 77 in FIG.7) over the exposed end of die substrate 84 in overlapping engagementwith the container 88.

A pre-sintered compact as described above may be loaded into a pressingassembly (such as reaction cell 30 in FIG. 3), placed in a press (suchas cubic press 20 in FIG. 2), and then subjected to a HPHT process fortimes sufficient to produce polycrystalline bonds between ultrahardmaterial particles and bond the ultrahard material 82 to the substratematerial 84. For example, during the pressing process, the loadedcontainer assembly may be subjected to pressures as high as 5-7 GPa andtemperatures as high as 1350-1600° C. The loaded container assembly maybe subjected to a predetermined pressure, then the temperatureincreased, and then the pressure further increased to a desired pressureand maintained there for a time sufficient for the ultrahard materialparticles to form polycrystalline bonds. The temperature is thenreduced, the pressure slowly released, and the resulting compact removedfrom the press. Operating conditions for several different pressingoperations are well known in the art and those skilled in the art willappreciate that the above description is only one example, and not alimitation on the invention.

Oversizing the ultrahard material relative to substrate material for acompact in the pre-sintered state, advantageously, can result in theproduction of an ultrahard compact having near-net shape geometrydirectly from the press that requires less material removal to obtain afinished product of desired form.

FIG. 9 shows one example of an ultrahard compact formed in a cubic pressusing a container assembly similar to the one shown in FIG. 8. After thepressing process, the reaction cell (similar to 30 in FIG. 1)surrounding the assembly is cracked opened and the loaded containerassembly (similar to 50 in FIG. 5) containing the sintered compact isremoved. The container assembly (50 in FIG. 5) is then removed from thecompact, by grinding. The container material can be easily and quicklyremoved from the surface of the compact due to its relatively softstructure compared to the ultrahard material used for the grindingoperation. After the container assembly is removed, an ultrahard compact90 as shown in FIG. 9 is obtained. The resulting compact has anout-of-press geometry very close to the near net shape desired for thefinal product.

An ultrahard compact 90 as shown in FIG. 9 was formed in a pressingprocess similar to a pressing process used to produce the compact 40illustrated in FIG. 4. However, the compact 40 in FIG. 4 was formedusing a conventional metal container having cylindrical side walls ofuniform diameter along the length. A container assembly similar to theone shown in FIG. 5 was used to form the compact 90 shown in FIG. 9.Comparing the out-of-press geometries of compact 90 with compact 40 inFIG. 4, it was found that forming a compact in accordance with anembodiment of the present invention can, advantageously, result in anout-of-the-press geometry that is closer to a desired net geometry(indicated by lines 93 in FIG. 9) than that of a compact formed using aconventional container (desired geometry indicated by and lines 46 inFIG. 4). Forming ultrahard compacts in accordance with one or moreembodiment of the present invention, advantageously, can reduce theamount of material required to be removed (91 in FIG. 9 versus 48 inFIG. 4) to produce a desired final geometry. The material to be removed(91 in FIG. 9) can be centerless ground to obtain a desired geometry (93in FIG. 9) at a substantially cost savings compared to material to beremoved (48 in FIG. 4) for conventionally formed compacts.

In accordance with one or more embodiments of the present invention, thematerial to be removed from a cutter formed using a conventionalrefractory metal container can be significantly reduced by reconfiguringtoe container to form the compact material prior to sintering inaccordance with an embodiment of the present invention. One or moreembodiments of the present invention allow for the radial placement ofadditional ultrahard material in the ultrahard material region of acontainer to compensate for shrinkage; that occurs in the ultrahardmaterial layer during sintering. As a result, an ultrahard compact ofnear net shape can be produced from the press and the amount of materialto be removed can be significantly reduced, resulting in a saving inmanufacturing output time and grinding wheel cost. By producingultrahard compacts in accordance with an embodiment of the invention,the amount of materials used to form compacts, the number of diamondwheels required to produce compacts, and the time for producing compactscan all be significantly reduced. Also, in one or more embodiments, bybulging the refractory metal container for forming an ultrahard compactwith a thick ultrahard layer in the region of the container that definesthe pre-sintered shape of the ultrahard material, the need forsignificant amounts of grinding due to the radial shrinkage of thematerial during sintering can be significantly reduced.

Additional Examples

Forming an ultrahard compact in accordance with one or more embodimentsdescribed above may be especially useful in the manufacture of compactshaving thicker ultrahard layers, such as ultrahard layers havingthicknesses of around 1.0 mm or more. In some cases, methods inaccordance with embodiment of the invention may be particularly desiredfor compacts having ultrahard layers that are around 1.5 mm or more inthickness.

In one or more embodiments, a container assembly may be configured toform a compact wherein the wall of the container in the first sectionextends outward further from a central axis than the wall in a secondsection by at least about 2% or more of the radial extent of the wall inthe second section. In one or more embodiments, the radial extent willbe less than or equal to 20% of the extent of the wall in the secondsection. Also, in one or more embodiments, the height of side wallforming the first section may be greater than 1.0 mm; although, theheight may vary around the container.

For example, container assemblies may be configured to form cylindricalcompacts within a product diameter range of 8 mm to 75 mm, and moretypically between 8 mm and 25 mm. The expansion diameters used to expandthe container assemblies in the ultrahard material forming region mayrange from about 2% to about 20% of the original diameter of thecontainer, which prior to sintering may be between 8 mm and 80 mm, andmore typically between 8 mm and 30 mm. In one or more embodiments, theradial expansion of a container in the ultrahard forming region of thecontainer is 2% to 12% the original diameter of the container (or of thediameter of the substrate to be placed in the container). That is, afirst section of the container assembly may be expanded or configured tohave a diameter (or radial extent) that is 102% to 112% of the diameter(Or radial extent) of the second section. Typically, the larger thediameter, the greater the expansion desired. Similarly, the greater thethickness of the ultrahard material, the greater the expansion desired.However, this may not be true in every case. In one or more embodiments,the first section may have an expanded section larger than 20% or moreof the radial extent of the second section, depending on the thicknessof the materials and material compositions.

In one or more embodiments, the magnitude of the radial expansion of theultrahard material section versus the substrate material section of acontainer will depend on the composition of the materials used to formthe compact as well as the press operating conditions. In general, theamount of the radial extent of the ultrahard material section comparedto the substrate section can be determined for manufacture of aparticular type of cutters by manufacturing a series of cutters usingdifferent container assemblies with ultrahard material sections ofdiffering radial extensions. For example, given a set of specificationsfor forming a series of compacts (e.g., product size, materialcomposition, ultrahard layer thickness, press type, etc.), a number ofcontainers having bulged sections of different radial expansion may beused, such as between 2 and 12% of the substrate diameter, increments of2%, and the resulting out-of-press geometries examined and compared todetermine a best container configuration to produce a desired compactnear net geometry after the pressing process.

Variables that may affect the expansion percentage desired in acontainer assembly include the product diameter, the ultrahard materialthickness, the press type, the pressing cell configuration (e.g., axialand radial proportions), and the ultrahard material composition (e.g.,such as average grain size, composition, metal content, etc.). Regardingthe press type, it has been found that higher axial loaded pressconfigurations typically require less expansion of the container becausedifferences between the radial shrinkage of ultrahard material andsubstrate material are typically smaller in these presses than in thosenot having as high of axial loads, such as cubic presses.

Referring to FIG. 10, in one or more embodiments a container assembly100 may include a container 105 with an end cap 107, wherein thecontainer is configured to include a first section 101 that tapersradially outward from a longitudinal axis 104 in a direction away from asubstrate forming section 103 to allow for a placement of ultrahardmaterial in the container 100 to compensate for an increased radialshrinkage that occurs in ultrahard material with distance away fromsubstrate material.

Although example container assemblies shown in figures are illustratedas two-part vessel comprising a container and an end cap, those skilledin the art will appreciate that embodiments of the invention are notlimited to any particular configuration. For example, in otherembodiments, a container assembly may include a vessel having at leastone opened end to allow for loading of compact materials in the vesseland a corresponding end cap adapted to mate with the at least one openedend to enclose materials in the vessel, wherein the vessel has sidewalls configured to define at least one first section and at least onesecond section in accordance with one or more embodiments describedabove. Referring to FIG. 11, in one or more embodiments a containerassembly may include a container 110 having openings at both ends 115and end caps (not shown) adapted to mate with each end of the container110 to enclose compact material loaded therein. The container 110includes side walls 117 adapted to form a contoured internal profilealong the inside length of the container 110 which generally outlines anultrahard material forming section 111 disposed between two substrateforming sections 113. The walls in the ultrahard forming section 111 arebulged outward with respect to the walls in the substrate formingsection 113 to permit placement of a radially larger mass of ultrahardmaterial between substrate materials to compensate for differences inradial shrinkage during sintering.

FIG. 12 shows another example in accordance with an embodiment of theinvention, wherein a container 120 includes a substrate forming section123 disposed between two ultrahard forming sections 121, which areconfigured to bulge outward with respect to the substrate formingsection 123 to allow for the placement of additional ultrahard materialon the substrate material to compensate for differences in shrinkageexpected during sintering.

Those skilled in the art will also appreciate that although thecontainer assembly shown in FIG. 5 is a generally cylindrically in shapeto form a generally cylindrical compact, in one or more otherembodiments, the container assembly may have any configuration to form acompact of any shape or geometry. For example, in one or moreembodiments, a container assembly may have a cross section that isgenerally triangular, rectangular, oval, or elliptic in shape to form agenerally triangular, rectangular, oval, or elliptic shaped compact.Additionally, a container assembly may be configured to form anon-axisymmetric compact. A container assembly in accordance with anembodiment of the invention may be configured to have an internalgeometry similar in form to any desired final geometry of the ultrahardcompact with at least one section therein for forming ultrahard materialexpanded radially outward with respect to another section therein forforming substrate material of a compact.

Those skilled in the art will also appreciate that in one or moreembodiments, a compact formed may include other materials, such as oneor more layers of transition material or interface barrier materialpositioned between the ultrahard material and the substrate material ofthe compact. Transition material may be placed in the first section, thesecond section, or in a designated transition section between the firstsection and the second section. Depending on the thickness, shrinkageand consolidation properties of transition material, the containerassembly may be configured to include a transition section specificallyconfigured to pre-form transition material to compensate for any radialshrinkage differences between the transition material and the othermaterials so that a compact of substantially uniform shape results aftersintering. For example, a container may be adapted to include a thirdsection having an internal profile distinguishable from the profile ofthe first section and the second section. The third section may beplaced between the first and second section, as desired, to provide ageometric transition between first section and the second section, suchas a profile that tapers from the radial extend of the first section tothe radial extent of the second section to provide a smoother geometrictransition between materials formed in the pressing process.

Also, in one or more embodiments, the radial extent of a first sectionmay be substantially constant along the length of the first section, asshown for example in FIG. 5. However, in other embodiments, the firstsection may have a radial extent that varies linearly or non-linearlyalong the length of the first section. One example of a linear variationalong the length of the first section is shown in FIG. 10, wherein thefirst section 101 has a reverse-taper profile that increases in radialextent from the longitudinal axis 104 in a direction away from thesecond section 103 to compensate for increases radial shrinkage inultrahard material with distance from substrate material. Thisconfiguration may be particularly useful for embodiments of theinvention involving compacts with very thick ultrahard layers, such aslayers greater than 2.0 mm in thickness.

Additionally, in other embodiments, ultrahard compacts may be made toinclude one or a plurality of masses of ultrahard material integrallyformed with one or more masses of substrate material. For example,ultrahard compacts may be formed for cutting tools or earth boring bitsto include one or more masses of ultrahard material sandwiched betweenor partially embedded in one or more masses of substrate material, suchas disclosed in U.S. Pat. No. 5,722,499 to Nguyen et al, titled“Multiple Diamond Layer Polycrystalline Diamond Composite Cutters,” andU.S. Pat. No. 6,272,753 to Packer, titled “Multi-layer, Multi-grade,Multiple Cutting Surface PDC Cutter,” which are both assigned to theassignee of the present invention and incorporated herein by referencein their entireties. Additionally, ultrahard compacts may be formed toinclude one or more masses of substrate material sandwiched between orembedded in masses of ultrahard material.

In the manufacture of multi-layer or multi-surface ultrahard compacts,the containers used to pre-form and sinter the materials may be formedto extend grater radially in one more sections on one or more sides ofthe container where ultrahard material is to be placed in comparisonwith sections where substrate material is to be placed to allow for theplacement of oversized ultrahard material on substrate material tocompensate for the differences in shrinkage and consolidation for thedifferent materials. Examples in accordance with this aspect of theinvention and discussed above are shown in FIGS. 11 and 12, wherein thecontainer side walls are configured to extend radially outward a greaterextent about the entire periphery of the container in one or moresections for forming ultrahard material versus the one or more sectionsfor forming substrate material.

In another example, shown in FIG. 14, a container for forming amulti-layer ultrahard compact includes a side wall expanded to extentradially outward along only a portion of the periphery of the containerto form ultrahard material, in a section of the container that will beembedded in substrate material. For the example show, the container isshaped to form a compact as shown in FIG. 13.

The compact 130, shown in FIG. 13, includes a substrate 136 with aprimary body of ultrahard material 132 bonded to a top surface of thesubstrate 136 and a secondary body of ultrahard material 134 forming astrip-like body embedded in the side surface of the substrate 136 adistance below the primary body of ultrahard material 132. The primarybody of ultrahard material 132 has a variable thicknesscircumferentially such that the thickness of the ultrahard material isgreatest along one side of the compact 130 designated as the leading orcutting edge. The secondary body of ultrahard material 134 is located onone side of the compact 130 below the cutting edge to provide an area ofincreased abrasion resistance for the compact 130. The secondary body ofultrahard material 134 spans a limited region of the compact's peripherywhere the increased abrasion resistance is desired most.

FIG. 14 shows a container in accordance with one embodiment of theinvention that may be used to form the compact shown in FIG. 13. Thecontainer 140 includes side walls 147 adapted to form a plurality ofultrahard material masses (at 141, 145) and substrate material masses(at 143) therein. Wall segments shaped to form ultrahard material (141,145) extend radially outward from the longitudinal axis 144 of thecontainer 140 a greater extent than wall segments shaped to formsubstrate material (143) so that radially larger masses of ultrahardmaterial can be placed in the container 140 with substrate materialprior to a pressing process to compensate for differences in radialshrinkage between ultrahard material masses and substrate materialduring the pressing process.

The container 140 includes a first section 141, a second section 143,and a third section 145 therein. The first section 141 and third section145 are configured to form ultrahard material, and the second section143 is configured to form substrate material. The first section 141 andthird section 145 extend radially outward a greater extent from thelongitudinal axis 144 than the second section 143. The extent of thefirst section 141 and the second section 143 may be the same ordifferent depending characteristics such as the thickness of thematerial to be formed in the section and the material compositions. Thefirst section 141 is adapted to form a primary mass of ultrahardmaterial (for 132 in FIG. 13) having a variable thickness about theperiphery of the compact. The height of the wall segment (i.e., lengthof side 147 parallel to the longitudinal axis) forming the first section141 adjacent the enclosed end of the container 140 varies about theperiphery of the container 140. The height of the first section 141 onthe first side 148 of the container 140 is greater than the height ofthe first section 141 on a second side 149 of the container 140. Thesecond section 143 is disposed adjacent the first section 141, betweenthe first section 141 and the third section 145 to form substratematerial.

The third section 145, is adapted to form a secondary mass of ultrahardmaterial (for 134 in FIG. 13), embedded in substrate material a selecteddistance away and generally aligned with the thicker portion of thefirst section 141. The third section 145 is positioned on the first side148 of die container 140 and is formed to span less than the entireperiphery of the container. The second side 149 of the container 140radially opposite the third section 145 is adapted to form substratematerial (indicated by 143). Thus, the third section 145 may bedescribed as a bulged section in the container wall 147 that spans alimited peripheral region of the container 140.

To form the compact shown in FIG. 13, the container 140 in FIG. 14 isprovided, but with the bulged portion of the third section 145 extendingall the way to the open end of the container 140 (indicated by dashedlines 146 a) to allow for the placement of a substrate having one sideloaded with an oversized mass of ultrahard material therein. First; thefirst section 141 of the container 140 is loaded with ultrahard materialparticles. The ultrahard material may be pre-pressed in the firstsection 141 to remove voids. Then, a substrate having a groove formed inone side and filled with an oversized mass of ultrahard materialextending laterally from its surface is aligned with the container 140and loaded therein. Then, the loaded container is pre-pressed in anelastomer die to force the walls 147 of the container 140 to form aroundthe compact material loaded therein. In particular, the pre-pressingoperation forces the bulged segment 146 a between the third section 145and the open end of the container 140 to form against substrate materialplaced in the container, to position 146 b, thereby trapping theoversized mass of ultrahard material in the third section 145 at thedesired location. An end cap (not shown) is then placed on thecontainer. The container may be further pre-pressed and then subjectedto a HPHT pressing process that results in formation of an ultrahardcompact as shown in FIG. 13. The container can be removed from thecompact and the compact ground to a final desired geometry as describedabove.

In view of the descriptions above, those skilled in the art willappreciate that other embodiments of the invention may be configured toform any desired compact. One or more embodiments of the invention maybe used to form a polycrystalline diamond compact primarily consistingof a polycrystalline diamond table bonded to a top surface of a tungstencarbide substrate. Additionally, ultrahard compacts formed in accordancewith aspects of the invention discussed above may be used as cuttingedges for cutting tools or cutting elements for drilling and rainingtools.

One example of a drill bit that may include a compact manufactured inaccordance with an embodiment of the invention is shown in FIG. 15. Inthis example, the drill bit 150 includes a bit body having one end 152adapted to couple to a drill string and another end including aplurality of blades 154 arranged to extend there from to engage withformation during drilling. A plurality of cutters 156 are mounted oneach of the blades 154 at selected locations and orientations to cutthrough formation when the bit 150 is applied to earth formations androtated under an applied load during drilling. The cutters 156 comprisepolycrystalline diamond compacts which include a mass of sinteredultrahard material (12 in FIG. 1) integrally formed with a metal carbidesubstrate (14 in FIG. 2). In this case, the ultrahard material ispolycrystalline diamond, and the metal substrate is tungsten carbideformed with a cobalt binder. The cutters 156 are brazed or otherwiseaffixed in pockets formed in the blades 154.

Embodiments of the invention may provide one or more of the followingadvantages. One or more embodiments of the invention advantageously mayprovide for the production of near-net shape compacts from the presswhich require less grinding to achieve a desired geometry. One or moreembodiments may be used to produce ultrahard compacts from a press thatcan be quickly centerless ground with less time required at the grindingwheel to achieve a final product of uniform shape. Producing compactsfrom a pressing process that have closer to desired geometries,advantageously, may reduce the output time for manufacturing ultrahardcompacts, and result in significant cost savings over conventionalmanufacturing techniques. Additionally, one or more embodiments of theinvention, advantageously, may also result in a significant cost savingsin grinding wheel costs because less grinding is required to produce afinal product. Also, forming near net-shaped compacts during; the HPHTprocess in accordance with one or more, embodiments of the inventionmay, advantageously, result in lower residual stresses in the compactmaterial, especially at the interface, in comparison to conventionalformed compacts. As a result, methods in accordance with one or moreembodiments of the invention may provide longer lasting compacts,cutting tools, and bits.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A pre-high pressure and high temperature sintered compact,comprising: a mass of ultrahard material; and a mass of substratematerial assembled with the mass of ultrahard material such that themass of ultrahard material extends an amount further from a central axisthan the mass of substrate material, and the mass of substrate materialextends to form at least part of a side surface of the compact, whereinsaid compact has not been exposed to high pressure high temperaturesintering.
 2. The compact of claim 1, wherein said mass of ultrahardmaterial forms a layer having a periphery and a first surface opposite asecond surface, wherein the first surface interfaces with the mass ofsubstrate material and wherein the periphery extends from the firstsurface to the second surface, and wherein when viewed in cross-sectionalong a plane through the central axis of said compact, at least at oneradial location as measured from the central axis, an entire peripherysection bounded by the first and second surfaces extends further fromthe central axis than the mass of the substrate material.
 3. The compactof claim 2, wherein the amount further is between about 2% and about 20%of an extent of the mass of substrate material from the central axis. 4.The compact of claim 3, wherein the compact is generally cylindrical inshape and has a diameter of between 8 mm and 80 mm.
 5. The compact ofclaim 3, wherein the mass of ultrahard material is at least 1.0 mmthick.
 6. The compact of claim 3, wherein the thickness of the mass ofultrahard material varies about the periphery of the compact.
 7. Thecompact of claim 3, wherein the compact has a cross section geometrygenerally comprising one selected from the group of circular, oval,elliptical, triangular, and rectangular in shape.
 8. The compact ofclaim 3, wherein the mass of ultrahard material is partially embedded ina groove formed in the mass of substrate material and formed to extendtherefrom.
 9. The compact of claim 3, wherein the mass of ultrahardmaterial is placed in a first section of a container, and the mass ofsubstrate material is placed in a second section of the container, and aside wall of the container extends further outward in the first sectionthan in the second section to form the ultrahard material.
 10. Thecompact of claim 3, further comprising an additional material disposedbetween the mass of ultrahard material and the mass of substratematerial.
 11. The compact of claim 3, further comprising a second massof ultrahard material adjacent to the mass of ultrahard material. 12.The compact of claim 11, wherein the second mass extends outward agreater distance from the central axis than the mass of substratematerial.
 13. The compact of claim 3, wherein the ultrahard materialcomprises one selected from the group of diamond and cubic boronnitride.
 14. The compact of claim 3, wherein the substrate materialcomprises tungsten carbide.
 15. The compact of claim 2, wherein whenviewed in cross-section along the plane through the central axis of saidcompact, at least at one radial location as measured from the centralaxis, the entire periphery extends further from the central axis thanthe mass of the substrate material.
 16. The compact of claim 15, whereinsaid mass of substrate material has a periphery, wherein along everyplane along the central axis extends a first radius having a firstlength as measured from the central axis to the ultrahard materialperiphery along the second surface and a second radius having a secondlength as measured from the central axis to the substrate peripheryalong an interface between the ultrahard material mass and the substratemass, wherein along each of said planes the first length is greater thanthe second length.
 17. The compact of claim 2, wherein said mass ofsubstrate material has a periphery, wherein along every plane along thecentral axis extends a first radius having a first length as measuredfrom the central axis to the ultrahard material periphery along thesecond surface and a second radius having a second length as measuredfrom the central axis to the substrate periphery along an interfacebetween the ultrahard material mass and the substrate mass, whereinalong each of said planes the first length is greater than the secondlength.
 18. The compact of claim 2, wherein the mass of substratematerial is an integral tungsten carbide substrate infiltrated with abinder.
 19. The compact of claim 1, wherein the amount the mass ofultrahard material extends from the central axis always increases in adirection away from the substrate material.
 20. The compact of claim 1,wherein the mass of ultrahard material extends further from the centralaxis about an entire periphery of the compact.